In a landmark intervention, elected leaders from every one of Yorkshire’s councils bar Rotherham and Sheffield have written to the Prime Minister Theresa May urging her to commit to an election for a mayor for the whole region within two years.

Under the proposal, submitted ahead of a crunch meeting between Yorkshire leaders and Communities Secretary Sajid Javid today, the council leaders agree that planned elections for a mayor for South Yorkshire should go ahead first.

The South Yorkshire election has been scheduled for May despite Barnsley and Doncaster having previously withdrawn from a devolution agreement for the Sheffield City Region.

However, now both Steve Houghton, the leader of Barnsley Council, and Ros Jones, the mayor of Doncaster, along with 16 other council chiefs signed up to the so-called One Yorkshire movement, agree South Yorkshire “should benefit from its devolution deal first” with a two-year mayoral term beginning after the planned May election.

Significantly, the letter from council leaders say this should in turn be followed by a “joint commitment” between the Government and local authorities in Yorkshire for an election in May 2020 “involving any councils who decide to join a Mayoral Combined Authority for the widest possible Yorkshire geography”.

The model echoes that proposed by Archbishop of York John Sentamu last year and leaves the door open for Sheffield and Rotherham to join the rest of the region in two years, as well as removing the need to overhaul the planned South Yorkshire election which is enshrined in law.

The letter has been sent to Mrs May, Chancellor Philip Hammond, Business Secretary Greg Clark and Mr Javid, who today prepares to hear from council leaders on their plans for a regional devolution. Members of the All Party Parliamentary Yorkshire and North Lincolnshire Group, including all of the region’s council leaders, MPs, peers and businesses and religious leaders, will meet at the House of Commons this afternoon.

The letter states: “We believe that there are many benefits to be gained from this approach by Government and the people and businesses of Yorkshire and therefore negotiations about the deal should start without delay.”

It says that with the Government’s support, tomorrow’s meeting “can seal an historic agreement about devotion to benefit all of Yorkshire’s five million people by potentially doubling the size of our economy”.